Method and apparatus for working soil samples

ABSTRACT

A method and apparatus for working soil samples to determine characteristics thereof. The soil is formed into a strand which is circular in cross section and the diameter of the strand is progressively reduced until the strand crumbles.

United States Patent Miller-Welt Feb. 22, 1972 [54] METHOD AND APPARATUS FOR WORKING SOIL SAMPLES r n s M [72] inventor: Hans Miller-Welt, Stuttgart, Germany UNITED STATES PATENTS [73] Assignee: Amtliche Forschungs-und Materialpru- 3,461,717 8/1969 Dunlap et al.. ..73/84 iungsantalt fur das Bauweaen, Otto-Grailnstitut an der Universitat Stuttgart, Stutt OTHER PUBUCATHONS gamvalhmgemGermany Kenny, The Complete Book of Pottery Making page 10 [22] Filed: n 25 1970 Greenberg: Publisher New York 1949 [21] Appl. No; 14,146 Primary Examiner-S. Clement Swisher Attorneywalter Becker Foreign Application Priority Data [57] ABSTRACT Feb. 24, 1969 Germany ..P 19 09 609.4 A method and apparatus for working soil samples to dew mine characteristics thereof. The soil is formed into a strand [52] 73/150 which is circular in cross section and the diameter of the [51] Int. Cl. ..G0ln 33/24 strand is progressively reduced until the Strand crumbles [58] Field of Search 73/432 R, 84, 87, 150,169;

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METHOD AND APPARATUS FOR WORKING SOIL SALES The present invention concerns a method of and device for ascertaining the rolling limit of soil samples according to which a test strand of at least approximately circular cross section is rolled until at a predetermined end diameter it breaks into crumbs. As rolling limit in the soil analyzing art is designated a specific limit in the consistency, namely a characteristic value for the state of transition at which a soil or soil sample in conformity with its water content changes from the plastic consistency to the semisolid crumbling consistency. The rolling limit, therefore, is physically defined as a relative water content of a soil sample when the latter is in the state of the above-mentioned consistency transition. The determination of the rolling limit is of considerable importance for underground work because the rolling limit furnishes important conclusions with regard to the load-carrying capacity and other loadability of the building ground while taking into consideration the water content. The carrying out of corresponding measuring tests of soil samples, therefore, forms an important part in the preparatory work for the construction planning. If desired, also further measuring tests may be carried out during the actual construction work due to the changed conditions in view of the removal of water or the like. The ascertainment of the rolling limit thus represents a measuring problem with a wide practical field of application.

Heretofore the ascertainment of the rolling limit was ef fected by rolling a soil sample of approximately 30 grams which sample was composed of a moist plastic mass of soil. The rolling was effected on a water-absorbent support by means of a plate, generally a glass pane or the like, and the sample was rolled so as to form a strandlike substantially cylindrical body with a fixed or predetermined end diameter of, for instance 3 mm. When during the rolling operation already prior to the predetermined end diameter the test strand started to crumble, the test was repeated with an increased water content of the sample. Generally, however, the conditions in practice are such that the end diameter starting with a water content of the soil within customary limits is reached during the first rolling cycle without encountering crumbling. In such an instance the test sample is immediately kneeded together again and is subjected to one or more further rolling operations until the crumbling, i.e., the plasticity transition, is obtained simultaneously with the predetermined end diameter of the sample. The numerical value of the rolling limit will then be obtained by determining the water content of the rolled test quantity by means of one of the customary methods employed for determining the moisture content of the soil.

The rolling of the sample has with this method a multiple function. In addition to the increase in the reduction of the diameter with the simultaneous decrease in the coherence of the strandlike test body up to the begin of the crumbling at a certain water content and diameter, the rolling brings about a continuous decrease in the water content due to air drying while the specific surface of the quantity of the test sample increases in opposite sense with decreasing diameter. The lastmentioned effect makes it possible normally, which means when the water content in starting condition is above the rolling limit, to determine the water content corresponding to the rolling limit. The drying operation must not occur too fast because otherwise the simultaneous obtainment of the end diameter and the crumbling, i.e., the corresponding water content, can be realized only under difficulties and in numerous repeated rolling operations. In view of unavoidable factors of uncertainty, the rolling is repeated and a medium value will be ascertained. The rolling with a decrease in the diameter results in homogenizing the spacial distribution of the water content within the test body in comparison to more compact test bodies. This homogenizing action is also of importance for an acceptable precision of the measurement.

The above remarks indicate that the way in which the rolling operation is carried out is important for the reliability and precision of the measurement and the possibility of reproducing the same. The heretofore generally customary manual method of rolling the sample under a manually loaded and moved plate, therefore, is dependent to a considerable extent on the practice and skill and the attention paid by the respective operator. For these reasons and also in view of the considerable work and time involved for the measuring operations, at mechanization and, if possible, automation of the rolling operation with its various functions if highly desirable.

It is an object of the present invention to provide such mechanization and automation of the rolling action for purposes of testing soil samples.

It is another object of this invention to provide a particularly simple device for carrying out the testing of soil samples.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 illustrates partially in side view and partially in section a rolling device according to the invention, said section being taken along the line Iq-Ia of FIG. 2, upper portion of FIG. l, and taken along the line Ib-Ib of FIG. 3, lower portion of FIG. ll.

FIG. 2 represents a horizontal section taken along the line II-II of FIG. ll.

FIG. 3 is a horizontal section taken long the line IIIIII of FIG. 11.

FIG. 4 is a diagrammatic simplified vertical section and partial view of a longitudinal rolling device according to the invention, said section being taken along the line IV-IV of FIG. 5.

FIG. 5 is a horizontal section taken along the line V-V of FIG. 4.

FIG. 6 is a horizontal section through a modified longitudinal rolling device according to the invention.

FIG. 7 is a diagrammatic side view of a transverse rolling device according to the invention with vertically succeeding roller pairs.

FIG. 8 is a horizontal section of the device of FIG. 7, said section being taken along the line VIIIVIII of FIG. 7.

FIG. 9 shows a modification of a transverse rolling device according to the invention with a plurality of successive rollers arranged within a drum.

FIG. I0 is a radial section through the device of FIG. 9, said section being taken along the line XX of FIG. 9.

FIG. 11 shows a still further embodiment of the transverse rolling device according to the invention with a roller in the interior of a drum and with cylindrically curved passages therethrough.

FIG. 12 is a side view of a transverse rolling device according to the invention with circulating endless belt.

FIG. 13 illustrates a particular embodiment of a supporting member for the endless belt of a transverse rolling device.

FIGS. M-ll6 respectively illustrate modified cross-sectional designs and arrangements of endless belts, supporting members and counter bearing surfaces for transverse rolling devices according to the invention.

FIG. 17 is a diagrammatic side view of an embodiment of a transverse rolling device according to the invention with two cooperating endless belts.

FIGS. lib-2d respectively illustrate three different embodiments of a transverse rolling device with disc-shaped rolling bodies and different radial profiles of the rolling surfaces at the end faces, said showing representing simplified axial sections.

The method according to the present invention, taking into consideration the customary manual method, requires that a substantially strand-shaped soil sample with at least an approximately circular cross section is rolled in the above-mentioned manner, and the method is characterized primarily in that the sample is rolled off on rolling bodies which at their contact areas with the sample carry out a movement which with at least one speed component is parallel to an axis of the sample. The sample advancing along its axis with decreasing cross section passes through an arrangement of roller bodies until the predetermined or desired end diameter has been reached. As rolling bodies for this purpose, principally rollers or rolls of cylindrical, conical or another mantle shape following a certain profile are employed in which connection it is merely important that the circumferential movement of the roller bodies will at the contact areas with the sample occur completely or at least with one component in the longitudinal direction of the sample so that an advancing movement of the strand-shaped sample body with a simultaneous decrease in its cross section and diameter is effected. Experience has shown that in view of such at least partially longitudinal rolling of the sample body, in addition to the advancing movement also the above-mentioned preceding functions of the rolling operation, namely reduction in diameter, drying, surface increase and homogenization, can be realized over a section of the sample body in a uniform manner and over a sufficiently long section of the sample body. In particular, the advantage is obtained in this connection that within the roller body arrangement there will be obtained a section of the passage or path of the strandshaped test body advancing in its longitudinal direction and that within said section the diameter or cross section of the test body will as to time and volume decrease uniformly. As a result thereof and in contrast to the customary manual method, according to which the test bodies are reduced over their length uniformly in cross section, the actual instant condition of the sample can be continuously observed within certain changing ranges. If that part of the passage or the roller body arrangement which corresponds to the predetermined end diameter is placed in this changing range, which is easily effected in any instance, it is possible at the respective location of the crumbling portion in the direction of movement ahead of or behind the end diameter to read the respective distance of the sample condition or of the water content at the crumbling area with regard to the rolling limit to be adjusted. Thus, if, for instance, the condition of the sample approaches the rolling limit from the moisture side, the crumbling area will with continuous passage and increasing drying of the sample and advancement in a direction opposite to the direction of movement enter the changing area and will approach the area of the end diameter. When this area is reached, the rolling limit is adjusted. By changing the advancing speed of the test body and, if desired, the drying speed, it is thus possible, in contrast to the customary manual method, to adjust the rolling limit in a continuous approximation. In this way a considerable reduction in work and time is realized, particularly in view of the otherwise frequently unavoidable working steps which do not lead precisely to the rolling limit, and also the possibility of reproducing the measurement and the precision of the measurement will be greatly increased.

When considering the above-outlined features of the rolling method according to the present invention it is possible to realize the predetermined end diameter for the test body by the rolling arrangement according to the invention in only one cycle or movement of the test body. This is highly advantageous when testing soil samples the starting condition of which is not too far away from the rolling limit and in which the testing operation is carried out at a relatively slowly increasing moisture during the rolling operation. In other instances, however, it may be more advantageous to reduce the test sample stepwise to the predetermined end diameter by passing the sample successively through roller arrangements in which the distance between the rollers decreases successively. This is advantageous in particular when starting with relatively moist samples. Moreover, the sample may, depending on the direction and the degree of deviation of the starting .condition from the rolling limit, be subjected to or treated with a drying or moistening medium while it passes through the rollers. In this way, it is possible practically to realize a fast and precise adjustment of the rolling limit.

A specific embodiment of the method according to the present invention is characterized in that the roller bodies roll on the sample with regard to the sample cross section at a higher tangential speed component and at a smaller axial speed component. In this connection, thus a combined longitudinal and transverse rolling of the strand-shaped sample can be realized, for instance, by means of rollers which are inclined with regard to the longitudinal direction of the sample. The particular advantage of this embodiment consists in the uniformly advancing reduction of the diameter and in the homogenization of the sample mass. In this connection it is advantageous to employ longitudinal rollers extending over the circumference of the sample while the mutual spacing of the rollers decreases in the advancing direction so that a passages is obtained which tapers toward the predetermined end diameter position. The occurrence and the displacement of the crumbling area can easily be observed.

The last-mentioned method can best be practiced by means of a device which is characterized primarily in that as rolling bodies there are employed at least three rollers which are distributed over the circumference of a substantially vertical passage for the sample and extend in the longitudinal direction of the passage. The axes of these rollers taper in the direction toward the lower end of the passage in a radial manner and are arranged so as to be inclined toward the vertical while being tilted about the lower roller ends in the direction of the circumferential speed of the rollers where they engage the sample.

A device of the above-mentioned type thus has a passage which tapers over the entire length while the spacing between the rollers distributed around the circumference of the sample permit the observation of the crumbling area as well as the access of a drying or moistening medium. Expediently, the rollers are joumaled with adjustable inclination in radial and/or tangential direction with regard to the passage. By a corresponding adjustment of the inclination and, if desired, change in the speed of the rollers, the rolling operation can be controlled within wide limits with regard to the desired gradual approach of the rolling limit.

Another embodiment of the method according to the invention is characterized primarily in that the roller bodies roll on the strand-shaped sample substantially parallel to the longitudinal direction of the sample. According to this method, substantially a longitudinal rolling with intensive kneeding of the mass of the sample takes place while generally it is necessary to do without a continuously tapering passage extending over the entire length. However, by employing rollers of greater diameters, it is possible also in this instance to obtain a uniformly tapering section of the passage with a corresponding possibility of checking the respective location of the crumbling area.

A device for carrying out the last-mentioned method is characterized in that as rolling bodies there are provided at least two rollers arranged at the level of the cross section of the at least approximately vertically extending sample. Preferably, the rollers are located in pairs opposite to each other and are adapted to roll on the sample in the longitudinal direction of the latter. This design has the advantage that also random and irregularly formed sample masses are without difficulties pulled by the rollers into the passage. The desired cross-sectional shape of the strand-shaped sample body to be formed can be realized, for instance, by designing at least two rollers arranged at the level of the cross section of the sample as profile rollers with arc-shaped, particularly concave mantle profile following a portion of a circle and extending at least around a portion of the circumference of the sample. Remaining voids or gaps in the mantle profile on the circumference of the sample may be closed by the arrangement of filling elements designed in conformity with the cross section of the sample and located in the voids or gaps between the profile rollers at the circumference of the sample. Expediently, with such a longitudinally extending roller arrangement, a plurality of sets of rollers at the level of the sample cross section are arranged successively in the direction in which the sample moves. These successive roller sets form passage openings with decreasing cross section. In order to save filling members or rollers, such filling members or rollers may be arranged around the circumference of the sample in a corresponding gap-free manner and preferably in the form of successive roller sets which in the circumferential direction of the sample are offset with regard to each other. The rolling in longitudinal direction while employing a corresponding device furthermore brings about the advantage that the course of the rolling operation and the cross section as well as the length and the tapering of the passage can be changed by simple means with regard to the adjustment of the rolling limit. This variation may be realized, for instance, by a simple change in the distance of the oppositely located rollers of a roller set and of the individual rollers from each other in the longitudinal direction of the sample.

The drawback of the customary hand-rolling method, namely the lack of a sample section with different diameters for observing the approach to the rolling limit while simultaneously the moisture content as well as the diameter of the sample are changed, can be reduced to a tolerable extent when the drying speed, starting from a corresponding sample moisture, is kept sufficiently low. In this connection it will be necessary to reduce the speed of the rolling operation or to repeat the rolling operation. In the emergency, with correspondingly repeated rolling operations, it is possible, so to speak, to feel oneself toward the rolling limit which is to be ascertained.

As already mentioned above, the object of the present invention, namely to create a device for mechanically carrying out the rolling operation, would therefore also be solved by a device which, in addition to bringing about a considerable technical advance while differing from the above-mentioned solutions according to the invention, would not have a spacial changing range of the diameter of the sample but would permit a fast carrying out of the rolling operation and thus, if necessary, a more frequent repetition of the rolling operation without requiring too much time and work.

The present invention furthermore comprises a device for ascertaining the rolling limit of soil samples according to which a substantially strand-shaped sample with an at least approximately circular cross section is rolled until it crumbles at a predetermined end diameter. Such device is characterized by two rollers which in circumferential direction of the sample roll on the sample while a gap is formed for the lateral passage of the sample. This means that with this device no longitudinal rolling or a rolling with a component in the longitudinal direction of the sample is involved, but an essentially exclusive rolling in transverse direction of the strand-shaped sample takes place. In this instance the strand-shaped sample is in contact with the surfaces of two cooperating rollers along corresponding mantle lines and is pulled into the bite of the roller pair, for instance, by gravity or by adhesion to the roller surface moving in the direction toward the bite while continuous transverse rolling of the sample its diameter becomes increasingly smaller. Expediently, when employing this method of advancing the sample by adhesion, the roller rotating in the direction toward the bite is driven at a circumferential speed which is somewhat higher than that of the counter roller. However, it is also possible by other means, for instance, by a different roughness of the surface of the rollers, to see to it that the practically always present slip between the sample and the roller surfaces of the roller rotating in feeding direction is less than that of the counter roller. When reaching the end diameter in conformity with the smallest distance between the roller surfaces, the sample leaves the device through the passage gap and conveyed to a moisture measuring station or after being kneeded together is subjected to a further rolling operation.

Principally, for the transverse rolling, it is possible to arrange the cooperating rollers adjacent to each other or one within the other. In the first-mentioned instance, a plurality of pairs of rollers is employed while the rollers of each pair rotate in the same direction and while the width of the bite decreases in the direction of movement of the sample. The width of the bite of the last roller pair corresponds to the predetermined end diameter of the sample. Such an arrangement of successive roller pairs expediently arranged along a vertical bite permits an automatic passage of the sample which may drop directly from the bite of one roller pair into the bite of the next following roller pair.

When the rollers are arranged one within the other, expediently one of the rollers is designed as a drum with an inner cylindrical mantle surface of a larger diameter whereas at least a further roller which at least temporarily rotates in a direction opposite to the direction of rotation of the drum and has a smaller diameter is arranged within the drum and is axis parallel or eccentric to the drum while forming with the mantle surface of the drum a gap for the passage of the sample. Such an arrangement has the advantage that the sample during the entire working operation remains in the interior of the drum and in a simple manner can from the starting side of the gap or from the last gap in case a plurality of successive roller gaps are employed be returned to the entrance side within the drum for repeating the rolling operation. Fundamentally, there also exists the possibility in this instance to form a passage defined by a plurality of successive gaps on the inner drum surface or in the form of a closed channel following the inner circumference of the drum and partially defined by a single inner roller. In the first-mentioned instance, expediently a plurality of rollers of small diameter are distributed over a circumferential section of the inner mantle surface of the drum which rollers together with the mantle surface of the drum form gaps the width of which decreases in the direction of movement of the sample.

The rollers of smaller diameter may be arranged, for instance, along a circumferential section of the mantle surface of the drum which circumferential section inclines in the direction of movement of the sample. The sample will then while being guided by the mantle surface of the drum likewise advance in the circumferential direction. of the drum from one gap to the next gap. In view of the greater adherence of the sample to the concave mantle surface of the drum, said lastmentioned surface is expediently employed as driving element which runs ahead of the circumferential speed of the smaller rollers.

In the second-mentioned instance, i.e., when a closed passage is formed, a single roller is employed in the interior of the drum. The outer mantle surface of the single roller forms with the inner mantle surface of the drum a passage which extends over the entire circumferential section and uniformly decreases in width for the sample in the circumferential direction. Preferably, an inner roller is employed which has a slightly shorter outer diameter than the inner diameter of the drum and is correspondingly less eccentrically arranged with regard to the axis of the drum. In this way, it is possible to form a slightly tapering curved and wedge-shaped or crescentshaped passage through which the strand-shaped sample passes while being continuously rolled and while continuously decreasing in diameter, the sample advancing in lateral direction. The feeding speed of the strand-shaped sample may be adjusted by correspondingly selecting the oppositely directed circumferential speed of the drum and roller for all desired values or pairs of values. This embodiment has the further advantage that also without slip, i.e., with a pure rolling movement or adhesion friction between sample and roller surface, it is possible to obtain the desired feed. The sample moves forward at half the difference of the circumferential speed of the drum and roller in the direction of the faster moving roller surface in the passage.

A further transversely rolling roller device forming part of the present invention is characterized by a circulating endless belt which has one belt section guided along a supporting surface and with the latter forms a passage for a sample rolling between the endless belt and the supporting surface. If desired, the supporting surface may be formed by a correspondingly arranged belt section which moves in opposite direction and pertains to a second endless belt. The magnitude and the direction of the feeding speed of the sample are in this instance determined by the differential speed of the two belts.

The operation of this design corresponds to that of the previously discussed designs while instead of a cylindrically curved passage there is employed a rectilinear passage with rolling surfaces which are moved in opposite direction with regard to each other. The device operating with endless belts is characterized by a simple construction and high working speed, while, however, as is the case with the last-mentioned design, the samples have to be fed in the form of strands or preformed pieces with an approximately circular cross section. This, however, generally causes no difficulties whatsoever. Also when employing an endless belt as roller surface, it is possible by means of a supporting member engaging the back side of the belt, which supporting member forms a corresponding angle with the supporting surface, to form a passage for the sample which passage decreases in a wedgelike manner.

Furthermore, the transversely rolling devices may, according to the present invention, also be so designed that the strand-shaped sample may during the rolling operation have its diameter varied within a certain range while corresponding means are provided for continuously adjusting the rolling limit. Such an arrangement can easily be realized when employing rollers or roller pairs engaging the sample along the mantle lines thereof. To this end, the axes of the respective rollers forming the bite may be slightly inclined with regard to each other or cross each other, or the roller mantles may be conical or in other suitable manner deviate from the cylindrical shape. This applies to two rollers arranged adjacent to each other and also to rollers arranged one within the other. At any rate, it is possible to obtain a sample with a diameter which varies over the entire sample or over a longitudinal section thereof. Corresponding remarks also apply to the transverse rolling devices with circulating endless belt and supporting member while the two last-mentioned elements are correspondingly inclined or profiled in the transverse direction of the belt. The supporting surface will then together with the endless belt form a passage the cross-sectional width of which measured perpendicularly with regard to the belt support is variable in the longitudinal direction of the sample. Another transverse rolling device which produces a range of variation in the diameter of the sample is characterized according to the invention in that a disc-shaped rolling body is provided which at its end face has an at least approximately plane rolling surface which rolls in the circumferential direction of the sample on the latter. This rolling surface together with an oppositely located at least approximately plane second rolling surface forms an annular disc-shaped closed passage for the sample which occupies a position which is substantially radial with regard to the axis of rotation of the rolling body. The second rolling surface may be stationary or with regard to the first rolling surface may be coaxial and may rotate in opposite direction thereto. The plane or frustoconical design may, if desired, also be replaced by another rotation symmetric contour with suitable radial profile, for instance, one with a radial profile which is concave to the said passage or is convexly curved or is undulated. The time-wise progressive reduction in the diameter of the sample during the rolling operation is realized by a corresponding progressive reduction in the spacing or the mutual pressing of the roller surfaces against each other.

With all rolling devices according to the invention, but in particular with the rollers arranged one within the other, with circulating endless belt or with designs operating with frustoconical rolling surfaces, the rolling surfaces or the corresponding building elements are for improving the possibility of checking the samples, expediently entirely or at least over portions thereof made of transparent material. In view of the low loads present during the rolling of soil samples, transparent synthetic materials or glass can be used without difficulties.

Referring now to the drawings in detail, the device according to FIGS. 1 to 3 shows a roller body arrangement 110 which comprises the approximately vertically journaled rollers 111 and forms a vertically downwardly tapering passage 120 for a strand-shaped sample which enters from the top. The axes of the rollers 111 are in conformity with the downwardly tapering cross section of the passage arranged so as to radially converge thereto and are additionally slightly pivoted with regard to the vertical about the lower roller ends and in tangential direction with regard to the cross section of the sample and, more specifically, in the direction of movement of the roller circumference at the points of contact between the sample and the roller surface. In view of this tangential inclination, the movement of the roller surface on the contacting points with the sample has in addition to a greater component of movement directed tangentially to the sample cross section, a smaller component which extends in the longitudinal direction of the sample and, more specifically, in the same direction as the direction of movement of the sample which means, according to the embodiment shown, a component which is directed downwardly. As a result thereof, the strand-shaped slightly conical sample is in addition to its tangential rolling movement on the rollers subjected to a feeding movement which is directed downwardly and toward the converging roller ends. Thus, the strand-shaped sample is when advancing along the passage rolled from the diameter of the upper cylindrical sample guiding means 131 to the intended end diameter in the lower sample outlet 151.

The sample inlet and outlet are in the particular example shown designed as cylindrical housing passages within the area of the head and foot mounting of the rollers and are coaxially arranged with regard to the passage for the sample. If desired, inserts with different bores for obtaining corresponding sample starting and end diameters may be provided for these housing passages. The sample mass, for instance, can by means of a hopper or the like be inserted into the sample feeding housing passage and during this step may be shaped into a strand.

The structural design of the device according to the invention comprises an upper and lower carrier or beam 130, 150 which beams are connected to each other by vertical supporting bars to form a housinglike framework. The end sections which protrude toward the right comprise the head mounting 138 and foot mounting 158 of the roller body arrangement 110 as well as the sample inlet 131 and the sample outlet 151. The upper carrier or beam has a common driving device 140 for the rollers 111. This driving device comprises a motor which through a chain drive comprising a chain 141, a pinion 146 on the motor shaft and a tensioning wheel 147 with tensioning means 148 (see FIG. 2) and driving wheels 142 is coupled to the upper end of the rollers while the chain 141 is in the manner shown in FIG. 2 looped around the driving wheels 142. The driving wheels 142 are mounted on the upper ends of intermediate shafts 143 respectively associated with the rollers. These intermediate shafts 143 form the joumaling for the head of the shafts and are connected thereto through the intervention of flexible or angle movable couplings 144. These couplings 144 have to absorb only slight deformations in view of the approximately vertical arrangement of the rollers 111.

The foot mounting 158 of the rollers which is arranged in the lower beam 150 is so designed that the rollers can be adjusted with regard to their radial inclination. To this end, in a manner shown in FIGS. 1 and 3, there are provided two discshaped coulisses 152 and 154 which are rotatable relative to each other about the longitudinal axis of the passage 120. These coulisses are provided with slotlike guiding paths 153, 155 which cross in pairs. In the particular example shown, the lower coulisse 154 is connected to the beam 150 so as not to be rotatable therewith, whereas the upper coulisse 152 is rotatably journaled in a flat centering portion of the lower coulisse. According to FIG. 3, the guiding paths 155 of the lower coulisse extend radially with regard to the longitudinal central axis of the passage whereas the guiding paths 153 of the upper coulisse extend tangentially and slightly curved in the manner of a spiral. The crossings 156 of the guiding paths may by turning the upper coulisse be displaced in radial direction whereby the radial inclination of the rollers can be changed accordingly. As will be seen from the drawing, the crossings 156 are engaged by plug pins 157 forming bearing means and being rotatably arranged in the bored end of a pertaining roller.

It is furthermore desired to be able to adjust the tangential inclination of the rollers independently of the radial adjustment, this may be realized by turning together both coulisses while a corresponding bearing arrangement is provided therefor. A certain interdependence between the radial and tangential adjustment may be realized in a simple manner by designing the course of the guiding path of the stationary coulisse so that it deviates from the radial direction.

In the particular embodiment shown, the upper rotatable coulisse 152 is provided with a downwardly directed sleevelike extension 159 which is rotatably joumaled in the beam 150. The central bore of said extension 159 simultaneously forms the outlet for the sample. The coulisse 152 is adapted by means of a dish spring 160 resting upon an abutment nut on the extension 159 to be held in the centering means for the coulisse 154. The sleevelike extension 159 is furthermore provided with a handle 161 which protrudes beyond the beam 150 and by means of which the coulisse 152 is manually rotatable so that the radial inclination of the rollers can be manually adjusted.

As diagrammatically illustrated in FIG. 1, between the supporting bars 125 of the device there is provided a blower 170 which by means of its funnel-shaped outlet 171 produces a dry airflow which is directed laterally against the passage 120 or the circumferential surface of the sample therein. If desired, the blower may comprise a heating device for producing a greater drying effect.

In operation of the device, the mass of the sample is by means of a funnel or hopper 115 mounted on the upper beam 130 (FIG. 1) and through the passage 131 brought into the passage 120 and deformed into a strand. The strand-shaped sample is by the rolling operation reduced in diameter so that finally the lower end of the sample reaches the lower roller ends and passes into and through the sample outlet 151 which the sample leaves with the intended end diameter or, depending on the radial adjustment of the lower end of the rollers, with a higher or lower intermediate value of the diameter.

When effecting the radial adjustment of the rollers to the end diameter, the adjustment of the water content of the sample in conformity with the rolling limit is effected expediently in conformity with a starting condition at which the sample has a relatively high water content with regard to the rolling limit. The lower end of the sample strand will then, when reaching the sample outlet 159, i.e., at the starting phase of the first passage during which expediently no great additional drying is carried out, not yet have reached the rolling limit and consequently the transition to the crumbling condition. During a further advancing drying and further passage of the sample mass, if desired while using drying air from the blower 170, the transition to the crumbling condition first occurs at the thinnest area of the sample, i.e., at the sample outlet 159. The crumbling area will with progressive drying of the sample move upwardly in a direction counter to the direction of movement of the sample. By a corresponding control of the rolling speed and, if desired, of the drying airflow, the crumbling area can be kept within the range of the sample outlet until a sufficient quantity of the sample mass is in crumbling condition at the end diameter. This sample quantity is then immediately conveyed to a measuring instrument of any standard type for ascertaining the water content and thereby the rolling limit.

The device according to the invention may furthermore be operated in such a way that first the outlet is adjusted for a sample diameter which is somewhat smaller than the intended end diameter. The crumbling area will then with increasing drying move from the lower end of the sample upwards along the sample and thus in the passage and will at the water content corresponding to the rolling limit just reach that level within the passage where the strand will have the intended end diameter. By gradually moving apart the lower roller ends up to the predetermined sample diameter and, if desired, by correspondingly controlling the drying operation, the crumbling area will then be caused to move downwardly. When the crumbling area has reached the sample outlet, the rolling limit has been reached. By such a continuous adjustment, a relatively high measuring precision can be realized.

When rolling samples with unfavorable deforming properties, it is possible, if desired, to work with an initially larger sample diameter and with a uniform radial feeding of the lower roller ends. If, however, the crumbling occurs prior to reaching the predetermined end diameter, the water content of the sample will have dropped already below the rolling limit so that it is necessary to reduce the drying operation or to interrupt the same or to increase the travelling speed of the sample which in its entrance condition is still sufficiently moist. If necessary, a remoistening has to be effected if it is not desired to discontinue the rolling operation and to repeat the test with a new sample.

Summarizing the situation, it is to be mentioned that by means of the device according to the invention it is possible to take into consideration over a wide range the quality of the sample and its moisture while obtaining a high measuring precision in a minimum of time for the rolling operation.

The embodiment illustrated in FIGS. 41 and 5 concerns exclusively a device for a longitudinal rolling. The sample mass 204 filled into a hopper 202 is rolled into a strand-shaped sample 200 with the cross section thereof decreasing in steps or sections. The sample moves in vertical downward direction through a roller system generally designated 210 which, according to the specific showing, comprises two sets of rollers 211 and 221 which at the respective height of a sample cross section are arranged in pairs and opposite to each other. These roller sets are offset with regard to each other in the direction of movement of the sample as shown in the drawing and are additionally offset by with regard to each other in the circumferential direction of the sample. As will be seen from FIG. 5, the rollers 211 and 221 are provided with a semicircular concave mantle profile and while the pairs of rollers are axis parallel, they have their cylindrical mantle sections arranged on both sides of the concave profile sections in mutual engagement with each other or they are arranged slightly mutually spaced from each other. Accordingly, the rollers 211 and 221 have their concave profile sections form passages 212, 222 with a cross section which decreases in the direction of movement of the sample so that the sample when moving through the roller set will decrease accordingly in diameter.

In view of the curvature of the mantle surface sections of the rollers in the direction of movement of the sample, it is possible with the embodiment of FIGS. 4 and 5 above and below the gaps between a roller set to form by means of the mantle surfaces of the rollers a closed passage extending over the circumference of the sample. In order nevertheless to realize a proper pulling-in of the sample mass into the gaps between the rollers, filling elements are arranged in these gaps between the profiled rollers along the circumference of the sample in conformity with the sample cross section. These filling elements 215 (FIG. 5) extend in a wedgelike manner at a slight distance from the roller mantle directly to the vicinity of the upper passage 212. The filling elements 215 are designed as correspondingly shaped extensions of the hopper 2112. A similar hopper 206, which receives the strand-shaped sample coming from the passage 212 and leads the same to the passage 222 which also has extensions acting as filling elements 225, is also provided for the lower roller set. At the exit side of the roller sets below the passages, special filling or guiding elements are generally not provided. With the exception of the inlet range of the roller sets, :in the embodiment of the device as shown in FIGS. 4 and 5, no sample section with uniformly decreasing cross section is obtained so that the possibility of a continuous adjustment or displacement of the crumbling area with the predetermined end diameter does not exist with this embodiment. When operating this last mentioned device, there exists a greater probability that the crumbling area will occur already during the first passage of the sample mass at a location of the sample strand which has not yet the predetermined end diameter which means that the rolling limit is prematurely reached. In view of the continuous moving operation, which also with the simplified device represents a considerable advantage over the heretofore customary method, the rolling operation can without interruption be continued while the drying is interrupted or a remoistening is effected. The sample section which is already too dry will thus immediately be removed from the device and still sufficiently moist sample mass will be moved into the passage. While the crumbling area can thus not be continuously brought into the predetermined end diameter, it can nevertheless relatively fast be brought into the range of the predetermined end diameter. In this connection, an adjustability of the roller sets with regard to their spacing in the direction of movement of the sample will be advantageous whereby the free sample length exposed, for instance, to the drying airflow and thus the degree of dryness can be adjusted. The drying speed must with regard to maintaining a sufficient homogenous distribution of the water content not be adjusted too high over the cross section of the sample. However, the equalization over the cross section of the sample, above all within the area of the smaller sample diameter, is generally effected at such a speed that the drying speed can be kept within a range which is suitable for the displacement of the crumbling area and for a control of the rolling limit.

With the device for a longitudinal rolling according to FIG. 6, two roller sets are provided each of which comprises three hollow profile rollers 241 and 251 uniformly distributed over the circumference of the sample. These roller sets are arranged in spaced relationship to each other and are offset with regard to each other in the longitudinal direction of the sample while additionally being offset with regard to each other in the circumferential direction of the sample. In this instance, there are present between the rollers of a roller set wider gaps at the circumference of the sample which gaps permit a radial adjustment of the rollers in the direction of the arrows. Filling elements are not provided. The longitudinal ribs which will form on the strand-shaped sample body are eliminated by the succeeding roller sets which are offset in circumferential direction. The radial adjustment of the rollers will, similar to the first-mentioned embodiment with a combined transverselongitudinal rolling device, permit a continuous control of the sample diameter intended for the rolling limit.

FIGS. 7 and 8 illustrate the fundamental principle of construction of a rolling device according to the invention for exclusively rolling in transverse direction. The strand-shaped sample 300 is in this instance laterally placed upon the mantle surfaces of two rollers 311 and 312 which rotate in the same direction and the axes of which are arranged at least approximately horizontally while their mantle surfaces at those areas which face each other form a passage gap 351 for the lateral passage of the sample. The sample is, on conformity with the arrows shown in FIG. 7, by friction with the rollers turned about its longitudinal axis while the rollers 311 and 312 thus roll in the circumferential direction of the sample on the latter. In this way, the sample diameter is progressively reduced until the sample can pass through the passage or gap 351. In the embodiment shown in the drawing, there is in downward direction provided a further pair of correspondingly arranged rollers 321 and 322 which form a gap 361 of reduced width and roll the sample to the predetermined end diameter. As will be seen from FIG. 8, the rollers 321 and 322 are conical and have their axes arranged in a horizontal plane so that the axes form an angle with each other. In this way a variable width of the gap 361 is obtained, and the sample 300 will likewise adopt a conical shape. In this way there is again obtained the possibility of continuously displacing and adjusting the crumbling area which, for instance,

in the range of the last roller pair moves from the thinner sample end into the sample body and by correspondingly controlling the drying speed can be kept at the desired diameter. Expediently, the rollers are so arranged that the said passage or gap at its narrow end will have a width which is less than the predetermined end diameter of the sample. Moreover, the roller spacing is adjustable by a variable arrangement of the roller bearing in conformity with the arrows indicated in FIG. 8. Also the convergence of the gap can consequently be controlled in conformity with the respective requirements.

The rolling arrangement shown in FIGS. 9 and 10 likewise works in conformity with the principle of the transverse rolling devices, however, one of the rolling surfaces is curved in a concave manner, namely the inner cylindrical mantle surface of a drum 411 of a larger diameter. ln conformity with FIG. 10, this drum is rotatably joumaled by means of a flange hub 464, 465 on a shaft 462 which is mounted in bearing supports 460 rigidly connected to the framework. The drum is by means of a belt drive 466 rotated in conformity with the direction of the arrow A shown in FIG. 9. Between the shaft 462 and the flange hub 465 of the drum there is independently rotatablyjournaled a hollow shaft 468 in the manner shown in FIG. 10. This shaft 468 is rotated by a further belt drive 470 and has that end thereof which extends into the interior of the drum provided with a pulley 472. The pulley 472 is adapted through the intervention of a further belt drive 474 in a manner shown in FIG. 9 to drive three rollers 412 of smaller diameter in conformity with the direction of the arrow B, said rollers 412 being located in an axis-parallel manner in the interior of the drum 411.

The rollers 412 are rotatably joumaled on shafts 414 which in their turn are by supporting flanges 416 rigidly connected to the shafts 462, which means are fixedly arranged with regard to the framework.

As will be seen from FIG. 9, the rollers 412 form together with the inner mantle surface of drum 411 the gap or passage 451. The width of the said gap decreases in the direction of rotation of the drum from roller to roller. The inner mantle surface of drum 411 as well as the mantle surfaces of the rollers 412 are conical as seen in FIG. 10. In this way, the gap 451 will have a correspondingly wedge-shaped cross-sectional shape with a width varying over the length of the gap.

In operation, a cylindrical preshaped sample body 400 is through a window 476 of the drum 411 inserted above the gap in an axis-parallel manner between the mantle surface of the uppermost roller 412 and the inner mantle surface of the drum 411. In view of the fact that the roller and the drum rotate in opposite direction with regard to each other, the sample is in conformity with the direction of the arrow C (FIG. 9) put into a rolling rotating movement. The circumferential speed of the mantle surface of the drum is expediently somewhat higher than that of the roller mantle surface so that the sample 400 while continuously rolling and decreasing in diameter is pulled into the uppermost gap. In this way, the sample will in the direction of the rotation of the drum successively pass through the successive gaps 451 up to the predetermined sample diameter. The sample will in this way, in view of the wedge shape of the gaps, take on a conical shape so that, similar to the preceding embodiment of the invention, a continuous adjusting possibility is obtained for the crumbling area within the sample body. Expediently, the drum is made of transparent material, for instance, a glass-clear synthetic material, or it may be provided with sight windows for observation purposes. This embodiment furnishes the advantage that a compact and closed structural shape is obtained while within the drum, drying and in particular moistening media may be employed.

FIG. 11 shows a modified transverse rolling device with rotating outer drum 511 the interior of which has a single larger roller 512 joumaled therein instead of a plurality of rollers rotating in a direction opposite to each other. The journaling of the drum 511 and the drive of the drum 511 and of roller 512 may be designed similar to the construction of FIGS. 9 and 10. Therefore, FIG. 11 has been shown more in the form of a diagram while details have been omitted.

Between the inner mantle surface of the drum 511 and the outer mantle surface of the roller 512, which latter is eccentri cally journaled with regard to the axis of the drum, there extends a closed passage 551 of a width which decreases in the direction of rotation of the drum over a circumferential section of the drum and roller. In other words, the passage 551 is with respect to its cross section confined on all sides. The insertion and removal as well as the observation or checking of a strand-shaped sample 500 is also with this device effected by means of openings or windows (not shown) in the drum 511. The said drum may again expediently be made of transparent material. Also with this embodiment, if desired, a slightly conical sample shape can be realized by a corresponding conical design of the mantle surfaces of drum and roller.

Starting from the above construction, constructions are also possible which within an outer drum have a roller which is concentrically journaled or driven but is eccentrically adjustable with regard to the drum. It is also possible to design the inner mantle surface of the drum and the outer mantle surface of the roller so as to be conical in the same direction. In the case of a concentric drum-roller mounting there is thus obtained a passage of a width which remains the same over the entire circumference but in the course of the rolling operation is adjustable uniformly up to the predetermined sample diameter. In connection therewith, it is likewise possible to obtain a wedge-shaped profile for the passage by correspondingly dimensioning the conical inclination or taper of the drum and roller mantle. Details of the construction and of the operation of such modifications can easily be derived from the above remarks with regard to the various illustrated embodiments of the invention.

Also the embodiment of FIG. 12 concerns a transverse rolling device, however, with a rectilinear passage 651 which is formed between the upper section of a circulating endless belt 611 (the drive therefor not being shown) and a supporting surface 612. As will be seen from FIG. 12, the supporting surface 612 is inclined with regard to the upper section of the endless belt whereby the width of the passage decreases in conformity with the rolling operation. At the upper and lower end of the supporting surfaces 612 there are provided adjusting devices 613 and 614 by means of which the width and the ratio of the cross-sectional decrease in the passage during the rolling operation can be controlled. At the bottom side of the endless belt there is provided a drying blower 605 which blows drying air onto the sample 601) located within the passage through the expediently permeable and gratelike endless belt. The upper section of the endless belt passes over a supporting member 652 which together with the supporting surface 612 determines the cross-sectional shape of the passage and which for treating the sample with drying air is expediently designed in the form of a grate or is permeable in any other convenient manner. In this connection it is also advantageous to design the confining elements of the passage, expediently the supporting surface 612 and the carrying means therefor, trans parent either entirely or partially so that the progress of the rolling operation and the start of the crumbling action can im mediately be observed.

The rolling device according to FIG. 13 differs from the preceding embodiment of the invention primarily in that the passage 660 is formed only unilaterally by a rigid element, namely a roller path 662, but on the other hand is formed by the nonsupported upper section 664 of a circulating endless belt. The sample 600 to be rolled is thus under a correspondingly easily adjusted tension of the endless belt on the path and during the rolling operation is in view of this pressing action uniformly rolled to a small diameter. In order to obtain a uniform distribution of the belt tension over the length of the path, the latter is designed so as to be curved convexly toward the endless belt.

Also with the rolling devices having an endless belt, it is possible by means of the embodiment illustrated in FIGS. 141 to 16 to obtain a noncylindrical sample with a diameter which changes uniformly over the length of the sample while the crumbling area can be correspondingly and continuously adjusted. According to the embodiment of FIG. 14, the inner side of the endless belt has arranged thereon a plane-supporting member 670, whereas the plane-supporting surface 672 forms an angle transverse to the plane of the supporting member 670 or the endless belt. Thus, a conically rolled sample 671 is obtained.

The embodiment according to FIG. 15 comprises a path 662 which as to cross section, i.e., in the plane perpendicular to the direction of movement of the belt and to the direction of movement of the sample as well as to the passage, is arched in a convex manner. Furthermore, there is provided a similar supporting member 6811 which is as to its cross section is arched in opposite direction. In this way there is obtained the indicated shape of a sample 684 which is uniformly constricted in its central area. Cor-respondingly inversely, with the embodiment of FIG. 16, there is provided a path 691 which toward the path or sample 694 is as to its cross section concave and equipped with a corresponding supporting member 609 which is arched in an opposite direction. With all of the above-mentioned devices, the crumbling area occurs with decreasing sample diameter first within a range of the length of the sample which has a small or the smallest sample diameter. With progressing rolling and drying, the displacement of the crumbling area up to the desired diameter can be observed and controlled. The checking is facilitated expediently by transparent supporting bearing surfaces or paths.

FIG. 17 shows still a further embodiment of a transverse rolling device according to the invention according to which two cooperating endless belts 696 and 698 are provided. Rigid supporting members and paths are not needed because the sample 699 rolls under tension between those sections of the endless belts which face each other. The directions of movement of the two last-mentioned belt sections in conformity with the direction of the arrows D and E in FIG. 17 are selected so that they are directed opposite to each other. In this way it is possible that the sample 699 can during the rolling operation by the same speed adjustment of the belts be held in unchanged position. Such a mode of operation will have important advantages in particular in connection with samples requiring a longer rolling time or a slowly progressing rolling operation. The upper endless belt 696 is in conformity with the arrow F tiltably journaled and is adapted to be folded or tilted upwardly for purposes of inserting or withdrawing the sample. For both endless belts there may be provided one and the same driving device 697.

Also the embodiments illustrated in FIGS. 18-20 are adapted to work in conformity with the principle of the transverse rolling. According to the embodiment illustrated in FIG. 18, there is provided a disc-shaped roller body 710 which with its shaft 713 is rotatably journaled in a frame 714. The roller body 710 is adapted to be rotated through the intervention of a belt drive 715. The lower end face 711 of the roller body is frustoconical and is approximately plane. The end face 711 forms together with a second, in this embodiment, completely plane frame-connected roller surface 712 an annular discshaped closed passage 751 with a wedge-shaped profile for the sample 71111 which rolls between the upper roller surfaces in circumferential direction. The sample 701) will accordingly during the rolling operation adopt a conical shape. For purposes of uniformly decreasing the diameter of the sample, the shaft 713 of the first roller body 7111 is journaled in a threaded sleeve 717 which latter can be adjusted in a corresponding thread of the frame 7141 by means of a hand wheel 716 and can be adjusted vertically.

According to the embodiment of FIG. 19, there are provided two coaxial disc-shaped roller bodies 721 and 722 which rotate in a direction opposite to each other. Those end faces 711a and 712a of the roller bodies 721 and 722 which face each other are of extremely flat conical shape in opposite directions and form a likewise annular closed passage 751a for the likewise conically journaled sample 7110. Both roller bodies are driven by belt drives 723 and 724 respectively. When the rotary speeds of the roller bodies are adjusted in an opposite sense, the sample can also in this instance during the rolling operation be held stationary at a point of the passage. Similarly, any desired slow movement of the sample in one or the other direction or in alternating directions can be obtained by a corresponding adjustment. Such rolling movement with alternating directions can be employed advantageously with the transverse rolling devices according to the invention and with the combined longitudinal-transverse rolling devices in order to obtain a more uniform deformation of the sample and a particularly sharply defined crumbling transition.

According to the embodiment of FIG. 19, the upper roller body 721 is in axial direction rigidly journaled whereas the lower roller body 722 comprises an adjusting device 800 in confonnity with an axially displaceably mounting. The adjusting device comprises a control motor 801, a pair of bevel gears 802, 803 and a threaded sleeve 804 which has a vertically displaceable shaft 726 and a bearing 728 thereon for the lower roller body 722 and also carries the roller body 722 and in its turn is rotatably journaled in the frame 805. Furthermore, there is provided an automatically working control device 810 for the reduction of the width of the passage 751a during the rolling operation. This control device has a feeler 811 which may operate, for instance, inductively and which feels a corresponding marking 730 of the bearing 728 which takes part in the vertical movement of the roller body 722. The feeler will when the predetermined adjustment as to height of the roller body 722 has been reached stop the control motor 801.

FIG. shows a modified roller body designed for a rolling device according to FIG. 18. The rolling surfaces 71lb and 7 12b which are located opposite to each other and pertain to the disc-shaped roller body have concave and convex sections pertaining to an axis symmetric radial profile. In this way also with transverse rolling devices equipped with disc-shaped roller bodies, it is possible to obtain a barrel-shaped longitudinal sample profile with continuously varying sample diameter and with a corresponding checking possibility as well as adjustability of the crumbling area. In a corresponding manner, if desired, also other longitudinal sample profiles can be obtained. Also with the last-mentioned transverse rolling devices, expediently at least one of the roller bodies is transparent for permitting a checking of the sample during the rolling operation.

Furthermore, the roller surfaces may be pressed against each other or against the sample by spring elements while special or separate feeding and advancing devices for the increasing reduction in the diameter during the rolling operation become superfluous.

It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawings but also comprises any modifications within the scope of the appended claims.

What is claimed is:

l. A method of determining the rolling limit of a soil sample which comprises: forming a strand from the soil sample which is circular in cross section, engaging the periphery of said strand, and progressively reducing the diameter of the strand until crumbling occurs, said strand being moved in the direction of the length thereof during the reduction of the diameter thereof.

2. A method of determining the rolling limit of a soil sample which comprises: forming a strand from the soil sample which is circular in cross section, engaging the periphery of said strand, and progressively reducing the diameter of the strand until crumbling occurs, the reduction of the diameter of said strand being accomplished in steps.

3. A method of determining the rolling limit of a soil sample which comprises: forming a strand from the soil sample which is circular in cross section, engaging the periphery of said strand, and progressively reducing the diameter of the strand until crumbling occurs, the moisture content of said strand being adjusted during the said reduction in diameter thereof.

4. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil working means comprising circumferentially spaced elongated rollers defining therebetween a channel which tapers inwardly from one end of the rollers to the other end thereof, drive means for driving said rollers in rotation, inlet means at said one end of said rollers for supplying soil to said channel, and outlet means for the soil at the said other end of said rollers.

5. A apparatus according to claim 4, in which said rollers at said one end are stationarily journaled in said frame and at the said other end are displaceable radially and circumferentially with respect to the axis of said channel.

6. An apparatus according to claim 5, in which said rollers at said other end comprise shafts extending axially therefrom, a first member having a first slot for each said shaft, a second member having a second slot for each said shaft, said first and second slots being inclined relatively, and means for rotating said first and second members relatively.

7. An apparatus according to claim 5, in which each roller at said one end thereof comprises an axial drive shaft, a sprocket on each drive shaft, a single drive element engaging all of said sprockets, and a drive motor for said drive element.

8. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil-working means comprising rollers arranged in sets spaced in the direction of movement of said strand, the rollers of each set rotating on parallel and coplanar axes and the axes of successive sets of rollers being disposed angularly to each other, the rollers of at least two successive sets of rollers being adjustable toward and away from each other, the channel defined by said sets of rollers decreasing in diameter in the direction of movement of said strand.

9. An apparatus according to claim 8, in which each roller has a groove formed in the periphery thereof and the grooves in the rollers of each set of rollers defining a substantially circular space for receiving said strand.

10. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil-working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil means comprising at least one pair of rollers defining a gap therebetween and adapted for receiving said strand at one side of said gap with the length of the strand parallel to the length of said gap, said strand passing laterally through said gap with simultaneous reduction of the diameter of said strand.

11. An apparatus according to claim 10, which includes at least two pairs of elongated rollers, each pair of rollers having a gap of a respective size therebetween, the rollers of each pair being rotatable in one and the same direction, said pairs of rollers receiving said strand laterally in the larger of said gaps and thereafter receiving said strand laterally in the smaller of said gaps.

12. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil-working means comprising a hollow drum, roller means inside the drum spaced radially from the inside wall of said drum and defining therewith a space which tapers in the circumferential direction of the drum, and means for driving said drum and roller means in respectively opposite directions.

13. An apparatus according to claim 12, in which said roller means is a single roller mounted on an axis displaced laterally from the axis of said drum.

14. An apparatus according to claim 12, in which said roller means comprises a plurality of rollers mounted on axes spaced circumferentially of said drum, said rollers and the inner surface of said drum defining said space, and means for driving said rollers simultaneously and in one and the same direction.

15. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil-working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil treating means comprising an endless belt, a first stationary member presenting a rolling surface facing a predetermined region of one reach of said belt, and a second stationary member presenting a support surface to the back of said belt in said predetermined region, said surfaces converging in the direction of movement of said reach of said belt.

16. An apparatus according to claim 15, in which at least one of said first members and said belt and second member is transparent.

17. An apparatus according to claim 15, in which the distance between said surfaces varies in the transverse direction of said belt.

18. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil-working means in the fonn of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil-working means comprising a pair of endless belts having reaches arranged in spaced relation to form a space for a soil sample, said belts moving in such a direction that the said reaches thereof move in respectively opposite directions.

19. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil-working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil-working means comprising coaxial relatively rotatable disc members adapted to roll a strand disposed radially therebetween in a circular path, said disc members defining therebetween an axial space which varies in axial dimension in the radial direction, at least one of said disc members being transparent.

20. An apparatus according to claim 19, in which at least one of said disc members in radial cross section between the axis and periphery thereof is concave toward the other disc member.

M. An apparatus according to claim 19, in which the said disc members are driven in relative rotation and the direction of relative rotation thereof is periodically reversed.

22. An apparatus according to claim 19, which includes adjusting means operatively connected to at least one disc member and operable when actuated to vary the axial distance between said disc members, and means operable during relative rotation of said disc members for periodically actuating said adjusting means.

23. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil-working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, and means resiliently urging said soil-working means toward each other.

24. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil-working means comprising an endless belt and spaced support rollers for the belt, a member forming a rolling surface spaced from one reach of said belt, said rollingasurface being convex toward said one reach, said one reach emg under tension so as to work a 801i sample disposed between said one reach and said rolling surface. 

1. A method of determining the rolling limit of a soil sample which comprises: forming a strand from the soil sample which is circular in cross section, engaging the periphery of said strand, and progressively reducing the diameter of the strand until crumbling occurs, said strand being moved in the direction of the length thereof during the reduction of the diameter thereof.
 2. A method of determining the rolling limit of a soil sample which comprises: forming a strand from the soil sample which is circular in cross section, engaging the periphery of said strand, and progressively reducing the diameter of the strand until crumbling occurs, the reduction of the diameter of said strand being accomplished in steps.
 3. A method of determining the rolling limit of a soil sample which comprises: forming a strand from the soil sample which is circular in cross section, engaging the periphery of said strand, and progressively reducing the diameter of the strand until crumbling occurs, the moisture content of said strand being adjusted during the said reduction in diameter thereof.
 4. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil working means comprising circumferentially spaced elongated rollers defining therebetween a channel which tapers inwardly from one end of the rollers to the other end thereof, drive means for driving said rollers in rotation, inlet means at said one end of said rollers for supplying soil to said channel, and outlet means for the soil at the said other end of said rollers.
 5. A apparatus according to claim 4, in which said rollers at said one end are stationarily journaled in said frame and at the said other end are displaceable radially and circumferentially with respect to the axis of said channel.
 6. An apparatus according to claim 5, in which said rollers at said other end comprise shafts extending axially therefrom, a first member having a first slot for each said shaft, a second member having a second slot for each said shaft, said first and second slots being inclined relatively, and means for rotating said first and second members relatively.
 7. An apparatus according to claim 5, in which each roller at said one end thereof comprises an axial drive shaft, a sprocket on each drive shaft, a single drive element engaging all of said sprockets, and a drive motor for said drive element.
 8. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil-working means comprising rollers arranged in sets spaced in the direction of movement of said strand, the rollers of each set rotating on parallel and coplanar axes and the axes of successive sets of rollers being disposed angularly to each other, the rollers of at least two successive sets of rollers being adjustable toward and away from each other, the channel defined by said sets of rollers decreasing in diameter in the direction of movement of said strand.
 9. An apparatus according to claim 8, in which each roller has a groove formed in the periphery thereof and the grooves in the rollers of each set of rollers defining a substantially circular space for receiving said strand.
 10. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil-working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil means comprising at least one pair of rollers defining a gap therebetween and adapted for receiving said strand at one side of said gap with the length of the strand parallel to the length of said gap, said strand passing laterally through said gap with simultaneous reduction of the diameter of said strand.
 11. An apparatus according to claim 10, which includes at least two pairs of elongated rollers, each pair of rollers having a gap of a respective size therebetween, the rollers of each pair being rotatable in one and the same direction, said pairs of rollers receiving said strand laterally in the larger of said gaps and thereafter receiving said strand laterally in the smaller of said gaps.
 12. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil-working means comprising a hollow drum, roller means inside the drum spaced radially from the inside wall of said drum and defining therewith a space which tapers in the circumferential direction of the drum, and means for driving said drum and roller means in respectively opposite directions.
 13. An apparatus according to claim 12, in which said roller means is a single roller mounted on an axis displaced laterally from the axis of said drum.
 14. An apparatus according to claim 12, in which said roller means comprises a plurality of rollers mounted on axes spaced circumferentially of said drum, said rollers and the inner surface of said drum defining said space, and means for driving said rollers simultaneously and in one and the same direction.
 15. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil-working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil treating means comprising an endless belt, a first stationary member presenting a rolling surface facing a predetermined region of one reach of said belt, and a second stationary member presenting a support surface to the back of said belt in said predetermined region, said surfaces converging in the direction of movement of said reach of said belt.
 16. An apparatus according to claim 15, in which at least one of said first members and said belt and second member is transparent.
 17. An apparatus according to claim 15, in which the distance between said surfaces varies in the transverse direction of said belt.
 18. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil-working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil-working means comprising a pair of endless belts having reaches arranged in spaced relation to form a space for a soil sample, said belts moving in such a direction that the said reaches thereof move in respectively opposite directions.
 19. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil-working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil-working means comprising coaxial relatively rotatable disc members adapted to roll a strand disposed radially therebetween in a circular path, said disc members defining therebetween an axial space which varies in axial dimension in the radial direction, at least one of said disc members being transparent.
 20. An apparatus according to claim 19, in which at least one of said disc members in radial cross section between the axis and periphery thereof is concave toward the other disc member.
 21. An apparatus according to claim 19, in which the said disc members are driven in relative rotation and the direction of relative rotation thereof is periodically reversed.
 22. An apparatus according to claim 19, which includes adjusting means operatively connected to at least one disc member and operable when actuated to vary the axial distance between said disc members, and means operable during relative rotation of said disc members for periodically actuating said adjusting means.
 23. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil-working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, and means resiliently urging said soil-working means toward each other.
 24. An apparatus for reducing the diameter of soil samples in the form of strands which are circular in cross section which comprises: a frame, soil working means in the form of at least two soil strand engaging members in said frame operable to receive a strand of soil and operable to reduce the diameter of said strand, said soil-working means comprising an endless belt and spaced support rollers for the belt, a member forming a rolling surface spaced from one reach of said belt, said rolling surface being convex toward said one reach, said one reach being under tension so as to work a soil sample disposed between said one reach and said rolling surface. 